Wednesday, November 4, 2015

Making some Supro-inspired guitar bridges.

A local musician for whom I've done a lot of work had an interesting little project for me this week. He picked up a Music Man Armada. We both agree it's nicely made, but he plays slide and found the string spacing a little challenging.

The high e is about 3/32" from the edge of the fretboard, and his slide bumps against it.

The spacing at the saddle needs to be adjusted. I can push it over by about 1.5mm and still keep the string over the polepiece of bridge pickup. We decided to file down the saddles and re-slot this bridge, but he asked if I'd be interested in making some non-adjustable rosewood replacements in the style of old 50's Supro and Airline guitars, one with a bone saddle, the other plain.

I took measurements from the stock bridge. Notice that the saddles aren't widely dispersed - this guitar has a compensated nut and so this bridge, though it might look "wrong", intonates very well.

I planed up a stick of rosewood.

And made up a quick cardboard template to mark spacing for the post holes and other measurements.

Drilling the post holes.

The Armada has a 12" fretboard radius. I used my sanding block to mark the curve on one of the blanks.

A little self-adhesive sandpaper and a minute of scrubbing roughed in the shape.

I marked the staggered saddle arrangement in pencil

The post holes provide a convenient way to affix the blank for carving.

I tried to leave a crisp knife-cut surface. The zig-zag effect isn't as dramatic as on some original bridges, but the intonation requirements play a part in the design.

For the second bridge, I needed to angled slots for the bone saddle inserts. Here's a useful trick. I applied masking tape to the side of the bridge, and to the edge of a piece of plywood. By applying superglue to the tape surfaces, I get a very strong bond, but when it's time to separate the two, they come apart easily and cleanly by sliding a pallet knife between them.

I mark a line that coincides with the distance between my 1/8" router bit and the edge of the router baseplate, parallel with the intended slot. I screw down a temporary fence, complete the routing, then repeat for the other slot.